This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Originally we sought to compare the same immunization protocol in both M. mulatta and M. fascicularis to determine if native viral protein, Tat alone could confer protection in either or both animal models. Although immunogenic, inactive Tat had not elicited protection against viral challenge in other studies;therefore it was important to determine if the active (native) molecule would be useful in vaccine design. Second, we wanted to determine if substitution of immunizations with Adenovirus recombinants encoding Tat followed by 2 Tat protein immunizations (Group II) is as effective as the multiple Tat protein immunization alone ( Group I). The ability of a vaccine to confer protective immunity with as few immunizations as possible is important, especially in the developing world. Third, we sought to evaluate two immunogens in combination, both aimed at blocking initial infection or early virus replication events, for their ability to blunt acute phase viremia (Group III). The immunogens were HIV Env and tat. Finally, cellular immune responses, especially to the SIV Gag protein, had been shown able to significantly reduce viremia in the chronic phase in the SHIV challenge model. Therefore, (Group IV) animals were immunized with gag protein. Together with appropriate control groups, these immunization regimens were to help elucidate and compare the response and protective efficacy of immunologically active viral gene products during immunization and after virus challenge.